Leaded fuel composition



Patented Feb. 19, 1952 assesco' LEADED FUEL oo PosI'rIoN.

William Q. Howell, Jr., Union,.N. J., assignor topmentr Company, acorpo- Standard Oil Develo ration of Delaware No Drawing.Application'March'l, 1950, Serial No. 147,139 7 This invention relatesto improved leaded motor fuels containing compounds known as leadscavenging agents. In accordance with the present invention the leadedfuel composition incorporates small quantities of lead scavenging agentsconsisting of a combination of halogenated hydrocarbons and tin alkylcompounds.

When fuels containing lead anti-knock agents are burned in internalcombustion engines, at least a portion of the lead anti-knock agent isconvertedinto a deposit of non-volatile lead compounds which accumulateson various parts of the engine. This deposit of non volatile leadcompounds contains a large proportion of lead oxide. Deposits of thisnature, due directly to the presence of the lead anti-knock agent in thefuel, are very undesirable, causing corrosion of the valves, failure ofspark plugs, and general deterioration of the engine parts affected. Toreduce this tendency of leaded fuels to form deposits on combustion, ithas been conventional practice to incorporate a lead scavenging agent inthe fuel. The mechanism apparently is that the scavenging agentconsisting of one or more halogenated hydrocarbons causes formation ofrelatively volatile lead halides during combustion which are largelyremoved from the combustion chamber through the exhaust port of theengine.

Heretofore the scavenging agents which have been employed have beenchosen from a wide variety of halogenated hydrocarbons. U. S. Patent1,575,444 suggests that the scavenger may consist of any halogencompound capable of combining with the lead during combustion; U. S.Patent 2,364,921 suggests that two to five carbon atom hydrocarbonscontaining three halogen atoms are suitable;

and more recently, U. S. Patents bons including hydrocarbons of 3 to 8carbon time the scavengers which are commercially emfployed in fuelsconsist of ethylene 'dibromide and ethylene dichloride.

of scavenger, in the case of aviation fuels, and not more than One andone-half theories for automotive fuels. One theory as defined as thequantity ofscavenger required to stoichiometrically combine with thelead present. Whilethe quantity of scavenger in some cases has beenincreased to as much as one and one-half theories 1 which vwill notreduce. atoms having from 2 to 3 bromine atoms and.

having a particular volatility. At the present 6 Claims. (Cl. 44-69) '2I for aircraft fuels also, it has been found'unde sirable to employ morethan one theory of scavenging agent in fuels of this type. This is truefor the reason that additional quantities increase the corrosion whichoccurs on engine parts, presumably due to the presence of halogen acids.For thesomewhat less critical conditions encountered in automotiveservice, one and one-half theories of scavenging agent are in generalpermissible, although even in this type of fuel it is undesirable to usemore than one and one-half theories. Furthermore, all scavenging agentsheretofore discovered, including those described in the aforementionedpatents, cause a distinguishable decrease in the anti-knock rating ofthe fuels in which the scavengers are incorpo rated. This proknockefiect of the scavenging agent becomes more and more marked as thequantity of scavenger increases, so that because of this factor again itis practically undesirable to employ more than one or one and one-halftheories of the conventional halogenated hydro:

carbons as-scavenger agents.

Because of this circumstance; that is, that the quantity of scavengingagent which may be em ployed is limited; scavenging efiects obtained arealso limited, leaving much to be desired. Thus in the case in which the,mostefiective halogen scavenging agent is employed in normal .concenoflead compounds are still encountered. 'f

It is, therefore, the principal object of this invention to provide anew and novel type of scav enging composition which will permit.utilization trations, substantial engine deposits consisting of morethan.theQ-bonventional quantityof scavringing-"agent, and which .willmore effectively.

freduc 2,479,900, U. S. 2,479,901, and U. S. 2,479,902 disclosepreferred types of halogenated hydrocaremploying scavenging: agents.

the, fuel to the extent normally encountered'when ancewith thisinvention-is to complement in the' action of a conventional.sc'av-'enger "wit/1 1 a olatile--'tin compound. ffFOlfexmample; a 'fue' lrnpolsitio n' chosen with regard to -:-this concept,'rnaycontainlonetheory ofragcon'fventionalhalogen scavenging agent together with analkyltin compound in such concentration as to give about 0.5 to. 1 /2-atomsof tin per atom of lead; It is presently'hypothesized. that oncombustion, lead 'halidesfiare' formed due to; the halogenscavenging-agent, but that formation of lead oxide is minimized by thepreferential lead deposits formed in an engine. burn v w I Itis afurther object of this 'f invention provide. ia scavengingcorr'p'osition e 1 anti-knock rating, ofi

,-.'rn *manner'byiwh cn theseobjectives areobvtainecl,".;in accordoxidation of the tin compound. Consequently, the conventional halogenscavenging agent, and the alkyl tin scavenging agent act together toreduce lead deposits by forming the maximum quantity of lead halide dueto the suppression of lead oxide formation. It is important to note thatneither the tin compound nor the halogen compound by itself is capableof providing the best lead scavenging action but that both materialsmust be present together to obtain the desired eifect.

As indicated the halogenated scavenging agents to be employed incompositions of this invention may be chosen from the long list ofsuitable compounds indicated by patents such as those described. Forexample, the conventional ethylene di-chloride and/or ethylene dibromidemay be employed, brominated xylenes may be employed, or other types ofbrominated aliphatic and aromatic hydrocarbons may be used. It ispreferred that the quantity of the conventional halogenated scavengingagent be about one theory, although somewhat more or less than thisamount can be used. However, one theory of the conventional scavengingagent is the quantity best adapted to provide optimum lead scavengingwith a minimum of engine corrosion due to the presence of the scavenger.

The tin compound to be employed may be deilned as a volatile tincompound. Beyond the fact that the tin compound should be reasonablyvolatile. for example having about the same volatility as the leadanti-knock compound, choice of the tin compound is not presently thoughtto be particularly critical. However, a preferred class of tin compoundsare the alkyl tin compounds having two to four alkyl groups, and havingalkyl radicals containing one to five carbon atoms. More specifically,the tin compound is preferably a tin alkyl compound having a volatilityin the range of about 300. F. to 500 F. This limitation as to the natureof the tin compound is a stringent limitation set by the distributioncharacteristics required in a multicylinder engine.

Thus it is well known that the quantity of lead anti-knock agent whichreaches a particular cylinder of a multicylinder engine may varyappreciably from the quantity reaching a different cylinder of theengine. For this reason it is important to select a tin compound havinga volatility closely similar to that of the lead antiknock agent inorder that a constant proportion of tin to lead may be maintained in allcylinders. It is presently contemplated that preferred tin compounds tobe used in the practice of this invention comprise those represented bythe following structural formula:

where R1, R2, R3, and R4, represent a hydrogen atom or alkyl groupshaving from one to four carbon atoms, and the total number of carbonatoms is not less than 8 and not more than 16. Thus, the followingcompounds typify but do not include all of those compounds conforming tothe foregoing formula; tetraethyl tin, tetrapropyl tin, tetrabutyl tin,dimethyl dipropyl tin, diethyl dibutyl tin, dimethyl ethyl propyl tin,diethyl dibutyl tin. Other alkyl tin compounds having less than fouralkyl substituents per molecule may also be used in the practice of thisinvention, as, for example, diethyl tin, triethyl tin, dipropyl tin.dibutyl tin, etc.

til)

While, as thus far described, the present inventlon has been concernedwith the addition of a volatile tin compound and a volatile halogencompound as separate substances, it is visualized that both the tinand'halogen compound may be incorporated in the same molecule, such as,for example, a halogenated tin alkyl or a tin haloalkyl. Thus, thetrialkyl tin bromides and dialkyl tin dibromides, as well as thetrialkyl tin chlorides and dialkyl tin dichlorides, would also besuitable for the practice of this invention. Materials of this type maybe represented by th formula:

Roi-X pounds of this type include dimethyl tin (ii-- bromide, dimethyltin dichloride, diethyl tin dibromide, diethyl tin dichloride, diethylpropyl tin bromide, diethyl propyl tin chloride, dibutyl tin dibromide,dibutyl tin dichloride, triethyl tin bromide, triethyl tin chloride,diethyl isobutyl tin bromide, and diethyl isobutyl tin dichloride.

Similar halogen-containing bivalent or trivalent tin compounds maylikewise be employed, such as ethyl tin bromide, diethyl tin bromide,ethyl propyl tin bromide, dibutyl tin chloride, ethyl propyl tinchloride, etc.

The other constituents of the fuel compositions of this invention areconventional. Thus, the base fuel may consist of virgin; thermallycracked; catalytically cracked; polymerized or alkylated hydrocarbonsand mixtures thereof boiling in the gasoline boiling range. Any gasolinetype fuel may be employed. The lead antiknock agent to be incorporatedin the fuel again may consist of any of the conventionally recognizedlead anti-knock agents. At the present time tetraethyl lead is thecompound which is generally employed, but other alkyl lead compounds maybe used, such as lead tetramethyl; lead trimethyl ethyl; lead dimethyldiethyl; lead methyl triethyl, or lead triethyl normal propyl. Thequantity of lead anti-knock agent is the quantity ordinarily used whichis generally in the range of about 0.5 to 4.6 cc. per gallon of fuel. Inaddition to these fuel constituents, other fuel additives may beemployed such as gum flux agents; solvent oils; dyes; gum inhibitors;lead stabilizers, etc.

As an example of the effectiveness of the concept of employing a tincompound to complement the action of a conventional lead scavenger, datawere obtained in actual engine tests to determine the amount ofcombustion chamber and engine deposits encountered when burningconventional fuels, and when burning fuel compositions of thisinvention. The conventional scavengers employed were those which arepresently used in commercial fuels, ethylene dichloride and ethylenedibromide. The motor gasoline employed was selected from commercialstocks and consisted of a blend of straight run, thermally cracked, andcatalytically cracked naphtha, having a boiling range of about 108 F, to378 F., and having an ASTM Motor Method octane number of 68, to whichwas'added 4 cc. per gallon of pure tetraethyl lead. A single cylinderLauson engine was employed in the tests, and runs were made for 40hours. At the end of the test period the total deposit found in thecombustion chamber was carefully removed and weighed. The portion ofthis deposit which consisted of lead was quantitatively determined byanalytical methods. Runs were made employing the base fuel andrespectively one theory of ethylene dichloride; one theory of ethylenedichloride plus one atom of tin (as tetrabutyl tin) per atom of lead;one theory of ethylene dibromide; and two theories of ethylenedichloride. The results of these tests are indicated in the table.

per gallon of fuel. From 0.5 to 1.5 theories, and preferably about 1.0theory of a halogenated scavenging agent are utilized, and from 0.5 to1.5 atoms, and preferably about 1.0 atom of tin is provided per atom oflead. The upper limit of tin concentration is particularly criticalsince a. greater concentration would exhaust the halogenated scavengingagent, resulting in an increase rather than a decrease in the amount oflead oxide deposit.

What is claimed is:

1. A leaded gasoline fuel containing in combination about 0.5 to 1theories of a halogenated hydrocarbon scavenging agent and a volatilealkyl tin compound, said volatile alkyl tin compound being present insuflicient proportions to provide from 0.5 to 1.5 atoms of tin per atomof lead.

2. The composition defined by claim 1, in which TABLE Eflect oftetrabutyl tin on lead scavenging eificzency l l'lltllileolry of I l'lheory i l Theory of 2 Theories of Deposit ll eights. EthvleneD1chlor1de+l Em ylene Ethylene Grams Dichloridc 2,5 2 DibromideDichloride Total Combustion (hamhcr l2. 5 7. 5 ll. 3 7. 7 Load inCombustion (hamher (By analysis) 7. 3 4. 6 G. 4 5. 2

l 0.17 vol. per cent tin tetrabntyl.

As indicated, by the data in the table, the presence of the alkyl tincompound decreased the total combustion chamber deposit by and promoted37% more scavenging of lead than in the case in which ethylenedichloride alone was employed. It is particularly significant that thecombustion chamber deposit was materially decreased when the tincompound was employed, as compared to the case when ethylene dibromidealone was used, since ethylene dibromide represents one of the mostpotent of scavenging agents when used alone. The results obtained withthe fuel containing the tin compound were also appreciably better thanthose obtained when employing two theories of ethylene dichloride, wherethe combustion chamber deposit was 7.7 grams total and 5.2 grams oflead. It should be appreciated that the use of such a high proportion ofethylene dichloride or ethylene dibromide is detrimental to engine life.For example, increasing the proportion of ethylene dibromide from 1.0 to1.5 theories has been reported (ASTM bulletin No. 154:53-6 (1948)) toincrease spark plug failures in aviation engines by 115% andto causesevere corrosion of exhaust valves and valve seats. The test on the fuelcontaining the volatile tin compound, on the other hand, showed that noappreciable increase in harmful spark plug and exhaust valve depositsoccurred, nor was any other condition of the engine adversely affected 5by inclusion of the tin compound.

As indicated, therefore, the compositions of this invention embraceconventional motor gasoline fuels containing lead anti-knock agents, aconventional halogenated hydrocarbon, and a volatile tin compound. Thisfuel composition is suited for use in internal combustion engines topermit minimum deposit formation. Preferably about 0.5 to 5.0 m1. oftetraethyl lead, or other lead alkyl anti-knock compound, are employedthe volatile tin compound has the general formula:

tetraethyl lead, 0.5 to 1.5 theories of a halogenated hydrocarbonselected from the group consisting of C3 to C3 mono and dibromohydrocarbons, and an alkyl tin compound having a boiling point in therange of 300m 500 F. and present in a quantity to provide from 0.5 to1.5 atoms of tin per atom of lead.-

4. The composition defined by claim 3 in which the said alkyl tincompound is selected from the group consisting of alkyl tin compoundshaving 2 to 4 alkyl radicals, containing a total of 8 to 16 carbonatoms.

5. The composition defined by claim 3 in which the said tin compound istetrabutyl tin.

6. A leaded gasoline fuel containing about 1 theory of halide and about1 atom of tin per atom 5 of lead.

WILLIAM C. i-IOWELL. JR.

REFERENCES orrEn The following references are of record in the 0 file ofthis patent:

UNITED STATES PATENTS Number Name 7 Date I 1,575,444 Midgley Mar. 2,1926 2,151,432 Lyons et a1 Mar. 21, 1939 Calingaert et a1. Aug. 23. 1949

1. A LEADED GASOLINE FUEL CONTAINING IN COMBINATION ABOUT 0.5 TO 1THEORIES OF A HALOGENATED HYDROCARBON SCAVENGING AGENT AND A VOLATILEALKYL TIN COMPOUND, SAID VOLATILE ALKYL TIN COMPOUND BEING PRESENT INSUFFICIENT PORPORTIONS TO PROVIDE FROM 0.5 TO 1.5 ATOMS OF TIN PER ATOMOF LEAD.